Purification and Chemical Composition of Reticulate Bodies of the Meningopneumonitis Organisms

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Abstract
Reticulate bodies of the [psittacosis-lymphogranuloma-trachoma] meningopneumonitis (MP) microorganisms were purified from L cells 18 hr. after infection by the combination of differential centrifugation in 30% sucrose solution and potassium tartrate density gradient centrifugation. It was ascertained by electron microscopy that purified preparations of reticulate bodies obtained were almost entirely free of host-cell components and of infectious elementary bodies of MP microorganisms. Purified reticulate bodies were easily disrupted by mechanical agitation, and it was observed in shadowed preparation that rlbosome-like particles 15 m[mu] in diameter were scattered from broken reticulate bodies. In shadowed preparations, reticulate bodies were found to range in size from 1.0 to 1.6 [mu] in diameter, but in cross-section the range was 0.5 to 1.0 [mu]. In these preparations, the purified reticulate bodies were irregular in shape, round or oval, and were composed of rather homogenous, amorphous, or reticulate material with moderate density. Some particles exhibited a less-dense internal structure, in which a coarse fibrous retlculum was seen. Chemical fractlonatlon of p32 -labeled purified reticulate bodies showed that they contained three times more ribonucleic acid (RNA) than deoxyribonucleic acid, with the RNA being composed primarily of 21S, 16S, and 4S RNA. No infectlvlty of purified reticulate bodies could be demonstrated.